All the goals came in a five-minute spell just before half-time and, although Barnet improved in the second-half, they never threatened to get back into it.
The visitors did hit the bar through a Jason Norville free-kick and, despite a triple substitution on the hour by manager Paul Fairclough, it had no bearing on the result.
Grimsby were quickly out of their blocks at the kick-off and put a shaky Barnet defence under pressure. Shots reigned in from all angles although Grimsby's rhythm was temporarily disrupted just after the half-hour when they lost leading scorer Michael Reddy through injury.
But Grimby's first-half domination was finally rewarded after 39 minutes.
The Barnet defence looked for an offside flag when the ball broke kindly to Grimsby striker Gary Jones. But the Grimsby number 19 kept his composure and beat keeper Matthew Reed from 12 yards.
The cheering hardly died down when a free-kick broke to Jones who stabbed the ball from close range for his second of the game.
The scoring was completed a minute from the break and the third in five minutes when outstanding midfielder Paul Bolland scored his first goal at Blundell Park this season with a cool finish.
The result means that Grimsby consolidate third place and nicely improve their goal difference while Barnet's away day blues continue.
The Bees have now not won in 16 away games and manager Fairclough has a massive task on his hands and knows that their home form more than ever is going to keep them in the Football League.
Grimsby now go into the away match against Rochdale on Tuesday knowing that victory would leapfrog them over Wycombe in second place.